A major part of our work has been studying the cellular basis somatosensory coding. We have concentrated on small subsets of trigeminal and dorsal root ganglion neurons expressing TRP-ion channels and have used a variety of screening techniques to explore the molecular architecture of these neurons. In this reporting period we identified,characterized and reported our findings on the neuropeptide Nppb. We discovered that Nppb is a primary transmitter of itch sensation. This peptide is released at the periphery and activates a central itch pathway that is selectively tuned. Additional experiments demonstrated a second neuropeptide, GRP, is downstream of Nppb. In a different set of studies, we examined the sensory cells required for mammalian thermosensation. Our work demonstrates that TRPV1- and TRPM8-expressing cells are hot and cold receptor neurons respectively. Furthermore, we established that afferent input from these cells combines to generate the sensation of warmth. Lastly, we found that a third separate population of neurons defined by the expression MrgD are responsible for responses to noxious temperatures.